import java.util.*;
/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 26727
 * Date: 2024-01-27
 * Time: 21:54
 */
class MyStack {
    private Queue<Integer> queue1;
    private Queue<Integer> queue2;
    public MyStack() {
        queue1 = new LinkedList();
        queue2 = new LinkedList();
    }

    public void push(int x) {
        if(!queue1.isEmpty()) {
            queue1.offer(x);
        }else if (!queue2.isEmpty()) {
            queue2.offer(x);
        }else {
            queue1.offer(x);
        }
    }

    public int pop() {
        if(!queue1.isEmpty()) {
            while(queue1.size()-1>0) {
                queue2.offer(queue1.poll());
            }
            return queue1.poll();
        }else if (!queue2.isEmpty()) {
            while(queue2.size()-1>0) {
                queue1.offer(queue2.poll());
            }
            return queue2.poll();
        }else {
            return -1;
        }
    }

    public int top() {
        if(empty()) {
            return -1;
        }
        if(!queue1.isEmpty()) {
            int size = queue1.size();
            int val = -1;
            for(int i = 0; i < size;i++) {
                val = queue1.poll();
                queue2.offer(val);
            }
            return val;
        }else {
            int size = queue2.size();
            int val = -1;
            for(int i = 0; i < size;i++) {
                val = queue2.poll();
                queue1.offer(val);
            }
            return val;
        }
    }

    public boolean empty() {
        return queue1.isEmpty() && queue2.isEmpty();
    }
}

